This invention relates to a lightning arrester device suitable for use in a gas insulation substation.
Enclosed lightning arrester devices of the conventional construction have comprised the grounded housing and the stack of superposed nonlinear resistors composed essentially of sintered zinc oxide and disposed therein. Since an electrostatic capacity developed between the grounded housing and each of the nonlinear resistors can not be disregarded with respect to that of each nonlinear resistor itself, there has been the disadvantage that the superposed nonlinear resistors unequally share the potential distribution at the applied commercial power frequency voltage so that those nonlinear resistors located on the incoming side have to bear the greater part of the voltage. Therefore the nonlinear resistors generate unevenly heat due to the commercial power frequency voltage and unevenly deteriorate in characteristics with the result that the lifetime of lightning arrester devices are much impeded.
In order to eliminate the abovementioned disadvantage, it has been alreadily proposed to extend an electrical conductor in the form of a rod or a plate from a high voltage side of the stack of the nonlinear resistors to run along and adjacent to the stack within the grounded housing. This measure has been effective for compensating for electrostatic capacities developed between the grounded housing and the nonlinear resistors thereby to cause the uniformity of a potential distribution along the stack of the nonlinear resistors superposed on and serially connected to one another.
Such a lightning arrester device has been generally vertically disposed and connected, for example, to the bus of gas insulation substations through a connecting electrical conductor extending therefrom. Accordingly the bus has been necessarily located above the device and therefore at a higher level. Alternatively, in order to decrease the height of the bus in view of the standpoint of the earthquake proof performance, the lightning arrester devices might be constructed to be suitable for installing them horizontally. This has resulted in an increase in floor area occupied by the devices suitable for extra-high voltages.
Accordingly, it is an object of the present invention to provide a new and improved lightning arrester device capable of being connected to a bus or a protected electrical appliance located at a lower level.
It is another object of the present invention to provide a new and improved lightning arrester device simple in both construction and assembly.
It is still another object of the present invention to provide a new and improved lightning arrester device most suitable for use in gas insulation substation and permitting the substations to be smaller in size and more economic than the prior art practice.
It is a further object of the present invention to provide a lightning arrester device having an improved structure suitable for connecting the device to a horizontally disposed bus.
It is a separate object of the present invention to provide a lightning arrester device having an improved structure by which a protected electrical equipment to be connected can be, as desired, disposed at a low position which lies within the height of the device proper and in which the maintenance and inspection of the lighting arrester device is easily effected.